"Rats need food, they need water and they need cover. They have got all the essentials here - it is a utopia for rats and we have seen rats on the site before and they are very difficult to eradicate.

"It is not so much what they eat, it is what they spoil.

"They spoil the grain through their urine and their droppings and it is unhealthy for folk to work in that.

"We have cracked the rat problem with rodenticides and now in one fell swoop the whole thing is going to be put back years."

Pest control expert, Mark Sheriffs, said: "Rodenticides are anti-coagulants, they work by making the blood haemorrhage - it is one of the only methods we have left to us to control mice and rats on rural farms."

The environment committee is due to vote on the ban early next month, before the full parliament votes in July.